Printing ink



Patented Feb. l9, 1935 UNITED STATES PATENT OFFICE No Drawing. Application January 10, 1931,

Serial No. 508,007

3 Claims.

5 printed on a sheet of paper or other suitable surface and a resinous powder is deposited on the paper before the ink dries, after which all the powder except that which adheres to the ink is shaken or blown off and the printed surface is subjected to heat to fuse the powder retained by the wet ink. This results in producing raised characters simulating the relief efl'ects produced with dies.

Most of the thernrographic printing now commercially produced lacks the permanency of the embossed or raised printing produced with dies. This is due in part to the character of the resins or gums employed and in part to the ink. The ordinary powders employed in thermography are apt to crumble if subjected to wear and are easily scratched or scraped off the paper. They are quite brittle and will readily crack or flake off when the paper is folded and creased. For this reason, they are not very satisfactory for use in letterheads which have to be folded or in other work that is subjected to wear.

So far, the only gum which has been found to give permanent results and which will not crack or peel is shellac. However, the use of shellac has been limited because of the special treatment it requires. Shellac will not adhere permanently to the paper if it is applied to an oil-base Most printer's inks 'are oil-base inks, that is, a large proportion of linseed oil or other oils enter into their composition. Most of the resins and gums used in thermography can be applied to printing with an oil-base ink, but when shellac is applied to an oil-base ink, it does not make a satisfactory bond with the paper and it may be readily flaked off, so that the result is a little better than that obtained with other gums. When a water-base ink is employed, on the other hand, the fused shellac adheres to the paper very tenaciously. However, waterbase inks are greatly affected by weather conditions. The ink must be maintained at a predetermined consistency in order to print properly and care must be taken to prevent it from drying too quickly. Usually, in winter time, when conditions of moisture and temperature can be readily regulated, there is little difficulty in using a water-base ink. But, in the summer time, the ink is greatly affected by heat and humidity and it frequently dries so quickly that it cannot be properly distributed upon the type. Alcohol or water is used to clean off the dried ink but these attack the composition rollers which distribute the ink and cause swelling of said rollers and hence they must be replaced with rubber rollers, which entails. considerable additional expense and inconvenience to the printer. However, if glycerine is used to prevent the ink from drying too rapidly it will attack the rubber rollers. Water-base ink has not the body of oil-base ink and its color is changed or faded when a reducing medium is employed therein. Furthermore, after the characters have been printed they must remain wet long enough to permit the powdered gum to adhere thereto. For these reasons it is often impossible to obtain satisfactory results with water-base ink 'in summer weather.

It is an object of the present invention to provide an ink which will not be affected by atmospheric conditions and which at the same time will be compatible with or will have an affinity for shellac, so that the fused shellac will adhere tenaciously to the paper or other material upon which it is applied.

Another object of the invention is to provide an ink for use in thermography which will not vaporize at normal atmospheric temperatures and which at the same time contains no oil.

Another object of the invention is to provide an ink having for its base an agent which is a plasticizer or at least a partial solvent of shellac, so that when the shellac is applied to the wet ink it will be carried by the liquid into the fiber of the paper and will be very firmly knitted thereto.

Another object of the invention is to provide an improved thermographic product in which the raised characters are extremely flexible and yet adhere tenaciously to the body on which they are printed.

Another object of the invention is to provide a thermographic product in which the characters are formed with rounded surfaces.

Other objects and advantages of the invention will appear hereinafter in connection with the following description of a preferred form of printing ink and the thermographic printing produced with such ink, and thereafter the novelty and scope of the invention will be pointed out in the claims.

I have found by considerable experiment that an ink may be formed which has for its base a derivative of butyl alcohol. Such an ink acts as a partial solvent for shellac and consequently will carry the shellac into the fiber of the paper, particularly when the shellac is subjected to a fusing heat. It is desirable, however, in an ink of this sort to select a material which has a comparatively high flash point since in the process of thermography the printing must be subjected to temperatures in the neighborhood of to degrees centigrade. The material must also be such as not to vaporize at normal atmospheric temperatures. I have found that the best results are obtained with dibutyl phthalate although other derivatives of butyl alcohol may be used, such, for instance, as metal butyl phthalate. Butyl stearate may also be mixed with dibutyl phthalate if desired. Other plasticizers of shellac may also be used, such as diamyl phthalate, tricresyl phosphate, triphenylphosphate and triacetin, and my invention includes the use of any plasticizer of shellac which has a high flash point and is not affected materially by atmospheric variations of temperature or humidity.

To give body to the ink I prefer to use a coaltar derivative, such, for instance, as paracumarone resin. While this material has proved to give the best results, I have also been able to obtain satisfactory results with other resinous substances, such, for instance, as mastics and dammar, etc. The purpose of the paracumarone resin is not only to give body to the ink, but also to give it the desired degree of viscosity.

A preferred ink embodying my. invention may consist of 100 parts by weight of paracumarone resin and 100 parts by weight of dibutyl phthalate with approximately 2 parts by weight of a suitable drier, such, for instance, as cobalt, acetate, lead linoleate or cobalt linoleate. To this may be added various dies or pigments to give color to the ink. If desired, I may replace 50 parts of dibutyl phthalate in the above formula with 50 parts of butyl stearate. The purpose of the drier is to cause a certain amount of oxidation which will limit penetration of the paper, thereby preventing offsetting or, in other words, to prevent the ink from passing through the paper an'd'showing on the reverse side. The resultant ink is substantially a non-drying ink. When it is impressed on paper it will remain moist for days. The ink has a strong affinity for shellac and when the shellac powder is applied thereto, it is partially dissolved thereby and enters with the ink into the paper. When the shellac is fused the moisture of the ink is absorbed by the powder insteadof being evaporated. This renders the shellac elastic and flexible. If desired a larger proportion of drier may be used, but I find that the proportion given above is satisfactory for average conditions.

When shellac is used with an ordinary waterbase ink the raised characters do not stand out in relief to the same height as characters produced with my improved ink. Also the characters as heretofore produced are flat and have more or less angular margins, whereas with my ink the characters are smoothly rounded, due to surface tension. This gives a pleasing effect more closely simulating the embossed efiects produced with dies.

An advantage of my improved ink over the inks heretofore used, is that it does not clog the type because it does not dry thereon. The ordinary oil-base ink produces a tough gelatinous film on the type which has to be removed from time to time with kerosene or other solvents. On

the other hand, the water-base ink is apt to dry upon the distributor plate and 1111 the type with carbon particles or other sediment constituting the body of the ink, so that frequent cleaning with alcohol or some other solvent is necessary. Since my improved ink is substantially a nondrying ink there is no possibility of producing a film on the distributor plate or the type or of clogging the same with sediment.

It will be clear from the above that my invention covers not only the provision of a novel printing ink for use in thermography, but also provides a new thermographic product. While the ink has been described as being particularly suitable for use with powdered shellac it may also be used with any of the other gums or resins that are now employed in thermography. Also, while I have described a particular derivative of butyl alcohol as a preferred base of my improved ink I wish it to be understood that I do not limit myself to this particular liquid, but have also used other chemicals either in the same family or of an entirely different family provided they act as plasticizers or at least partial solvents of shellac, will not vaporize at atmospheric temperatures, and have a flash point not below 100 degrees centigrade.

An advantage of my ink is that it has a strong aflinity for resinous surfaces and may be used for raised printing on phenolic condensate and lacquered materials. It is also adapted not only for use on paper, fabrics and wood but also provides a very firm bond for shellac on nonabsorbent surfaces such as metal and glass. Heretofore, it has been impossible to apply thermographic printing with shellac to glass or metal so that it would adhere with any degree of permanency. My invention, therefore, includes a new product, namely a glass or metallic base with raised permanent printing thereon.

While I have referred to my ink as having coloring matter therein, this is not essential when the ink is used in thermography. The shellac or other powdered gums may be colored or coated with metallic materials in which case a transparent ink may be employed.

Having thus described my invention what I claim as new and wish to cover by Letters Patent is as follows:

1. A substantially non-drying printer's ink adapted for thermography, said ink being composed of substantially equal parts by weight of a water insoluble resin as a body and a plasticizer as a base, said plasticizer being of the group consisting of dibutyl phthalate, butyl stearate, diamyl phthalate, tricresyl phosphate, triphenyl phosphate and triacetin.

2. A substantially non-drying printers ink adapted for use in thermography, said ink being composed of substantially 100 parts by weight of dibutyl phthalate as a base, 100 parts by weight of paracumarone resin as a body, and 2 parts by weight of a drier.

3. A substantially non-drying printers ink adapted for thermography, said ink being composed of substantially 100 parts by weight of paracumarone resin, 50 parts by weight of dibutyl phthalate, 50 parts by weight of butyl stearate, and 2 parts by weight of a drier.

ADOLF SCHNEIDER. 

